Author(s): Kyung Hyun Park, Hyun Do Jeong
A protein-bound polysaccharide preparation, PS-K, isolated from Curiolus uersicolor was evaluated for its ability to enhance resistance against Edwurdsiella rurdu, causal agent of classical edwardsiellosis in tilapia, Oreochromis nihicus. At a dose rate of 0.1 mg PS-K g- ’ body weight, maximal resistance was developed in fish 1 week after intraperitoneal injection. Enhanced resistance was first observed at 3 days and maintained for 21 days post-injection. Furthermore, oral administration of PS-K (0.1 mg g- ’ body weight) to fish daily for 21 days prior to an intraperitoneal challenge with E. tardu resulted in enhanced resistance, manifested as reduced mortality relative to controls. Intraperitoneal administration of PS-K 24 h after challenge with E. turdu also enhanced resistance and demonstrates the potential of PS-K as a prophylactic agent in aquaculture. In PS-K injected fish, increased phagocytic activity of pronephros cells against sheep red blood cells and rapid elimination of the bacteria from the blood and liver suggested that PS-K enhanced the resistance of tilapia to bacterial infection through the activation of the nonspecific immune system.